C# Program to Check Happy Number

Posted in C# Tutorial

Updated on Jan 11, 2024

By Mari Selvan

👁️ 57 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the domain of programming, certain mathematical properties and patterns are often explored. One such interesting concept is the notion of "happy numbers."

In this tutorial, we will delve into a C# program designed to check whether a given number is a happy number.

📄 Example

Let's take a look at the C# code that checks whether a given number is a happy number or not.

Program.cs

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using System;

class Program {
  // Function to calculate the sum of squares of digits
  static int SumOfSquares(int n) {
    int sum = 0;
    while (n > 0) {
      int digit = n % 10;
      sum += digit * digit;
      n /= 10;
    }
    return sum;
  }

  // Function to check if a number is a happy number
  static bool IsHappyNumber(int n) {
    int slow = n, fast = n;
    do {
      slow = SumOfSquares(slow);
      fast = SumOfSquares(SumOfSquares(fast));
    } while (slow != fast);

    return (slow == 1);
  }

  // Driver program
  static void Main() {
    // Replace this value with your desired number
    int number = 19;

    // Check if the number is a happy number
    if (IsHappyNumber(number)) {
      Console.WriteLine($"{number} is a Happy Number.");
    } else {
      Console.WriteLine($"{number} is not a Happy Number.");
    }
  }
}

💻 Testing the Program

To test the program with a different number, replace the value of number in the Main method.

Output

19 is a Happy Number.

🧠 How the Program Works

The program defines a class Program containing static methods SumOfSquares and IsHappyNumber.
The SumOfSquares method calculates the sum of the squares of digits of a given number.
The IsHappyNumber method checks whether a given number is a happy number using Floyd's cycle detection algorithm.
The Main method tests the program with a sample number (in this case, 19).

📏 Between the Given Range

Let's take a look at the C# code that checks for Happy Numbers in the specified range.

Program.cs

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using System;
using System.Collections.Generic;

class Program {
  // Function to check if a number is happy
  static bool IsHappy(int num) {
    HashSet < int > seen = new HashSet < int > ();

    while (num != 1 && !seen.Contains(num)) {
      seen.Add(num);
      num = GetNextNumber(num);
    }

    return num == 1;
  }

  // Function to get the next number in the iteration
  static int GetNextNumber(int num) {
    int result = 0;
    while (num > 0) {
      int digit = num % 10;
      result += digit * digit;
      num /= 10;
    }
    return result;
  }

  // Driver program
  static void Main() {
    Console.WriteLine("Happy numbers in the range 1 to 50:");

    for (int i = 1; i <= 50; i++) {
      if (IsHappy(i)) {
        Console.Write($"{i} ");
      }
    }

    Console.WriteLine();
  }
}

💻 Testing the Program

Output

Happy numbers in the range 1 to 50:
1 7 10 13 19 23 28 31 32 44 49

Simply run the program to see the happy numbers in the specified range.

🧠 How the Program Works

The program defines a function IsHappy that checks whether a number is a happy number or not.
Inside the IsHappy function, it uses a HashSet to keep track of numbers encountered in the iteration.
The GetNextNumber function calculates the next number in the iteration.
The Main function iterates through numbers from 1 to 50 and prints the happy numbers.

🧐 Understanding the Concept of Happy Number

A happy number is a positive integer defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1, or it loops endlessly in a cycle that does not include 1.

For example, let's take the number 19:

1²+9² = 82
8²+2² = 68
6²+8² = 100
1²+0²+0² = 1

In this case, 19 is a happy number because the process ends with 1.

🎢 Optimizing the Program

While the provided program is effective, there are various ways to optimize and enhance it further. Consider exploring different algorithms or incorporating additional features based on your specific requirements.

Feel free to incorporate and modify this code as needed for your specific use case. Happy coding!